Thoughts are one thing, actions are another.
If I have negative thoughts (and I have plenty of those, believe me) I wouldn't waste energy trying to suppress them. I let them live. However, I don't believe in keeping still when I'm in a state like that, because those negative thoughts will only gather momentum. I like to do something, anything, that is in some way positive.
For example, even if I wake up in the blackest of moods, I still put on my tracksuit and I go out running. The negative thoughts may still be there as I run, but I still keep on going regardless.
What I find is, when I get back home and get freshened up, I have a better perspective on things.
I've been out. I've done something. I've breathed fresh air. I may even experience a natural "high" from the exercise. It could be a combination of all these things. Who knows? But because I've done something, I don't feel so bad towards the end of the day.
I used sport as an example, but there are many other things you could do. Even if it's just housework, redecorating your house or fixing the car...just do something that has, in some way, a positive outcome.
It really helps me.